Miniature multiple unit variable resistor



1 1950 K. w. YOUNGBECK EI'AL 2,525,993

MINIATURE MULTIPLE UNIT VARIABLE RESISTOR 2 Sheets-Sheet Filed 001:. 6,1948 IN V EN TORS m B N an. R m 0 U 7 06 T .A W w LY RR A K W 17, 1950K. w. YOUNGBECK ETI'AL 2,525,993

MINIATURE MULTIPLE UNIT VARIABLE RESISTOR Filed Oct. 6, 1948 2Sheets-Sheet 2 INVENTORS KARL W.Youneesc K BY HENRY J. GwzcxsrsmATTORNEY Patented Oct. 17, 1950 MINIATURE MULTIPLE UNIT VARIABLERESISTOR Karl W. Youngbcck and Henry J. Glueckstein, Milwaukee, Wis.,assignors to Globe-Union Inc., Milwaukee, Wis., a corporation ofDelaware Application October 6, 1948, Serial No. 53,118

This invention relates to improvements in variable resistors, andparticularly to miniature multiple unit variable resistors.

Units of this type are used for hearing aids, telephone equipment, andin other electronic circuits where smoothness of operation, compactness,and small size are required characteristics. Resistors of this type maybe connected for tandem or dual (independent) operation. In either casethe problem is to arrange and hold together the variable resistor unitswithout using bulky or insecure fastening means and space-consumingcouplings.

' It is an object of this invention, therefore, to provide a miniaturemultiple unit variable resistor in which the units are secured togetherin coaxial arrangement in such fashion that a mini-.

able resistor in which the control knobs are so arranged and secured tothe control shafts of reing of an adjacent unit; and interconnecting thetie bracketswith the mounting brackets so as to hold the units as soarranged. To provide suilicient space for the inclusion of a connectingcoupling between the shafts of adjacent units there is positionedbetween the units a spacer disc which also functions as a cover platefor the open end of one of the units. This disc -is notched toaccommodate the mounting brackets and permit a flush fit of the units.When the unit is assembled for dual control, an inner control knob issecured to the shaft of the outer unit by a knob-locking clip and anouter control knob is secured to a coupling shaft which operates thisinner unit. This outer knob overlies and encloses projecting portions ofthe spaced arms on the knob-locking clip which hold the inner knob. Inthis way the space required to secure the knobs the appearance of theunit enhanced.

The novel featureswhich are considered chartion, itself, however, bothas to its organization 5'Claims. (Cl. 201) and its method of operation,together with additional objects and advantages thereof, will best beunderstood from the following description of a specific embodiment Whenread in connection with theaccompanying drawing, in which:

connecting the shafts of the variable resistor units;

Fig. 5 is a view partly in side elevation and and partly in crosssection of a dual control miniature multiple unit variable resistorembodying the present invention;

' Fig. 6 is an enlarged sectional view taken on the line 6-6 of Fig. 5;

Fig. '7 is an enlarged sectional view taken on the line 1-4 of Fig. 5;and

Fig. 8 is a perspective view of the coupling shaft by which dual controlof the resistor is obtained.

Referring to the drawings by reference nu- "merals, there is viewed inFig. 1 a tandem control miniature multiple unit variable resistor,generally designated ID. A dual control resistor H of this multipleunittype is viewed at Fig. 5. Both resistors consistof two variableresistor units having identical housings and substantially identicaloperating elements except for slight differences between the shafts ofthe front and rear unitsand between the shafts of the tandem and dual"types; As herein used, front or forward will betoward the right, andrear or back will be toward the left as viewed in Figs. 2 and 5.Each'resistor unit for both dual and tandem types comprises a housing l2having a base or rear wall with a centrally mounted shaft holding'bushing l4. Each housing also includes a peripheral side wall providingan opening at the front of the housing. The opening of the front unitis'normally closed by a washer type cover It and the opening of the rearunit by a spacer disc 46. The construction of the resistor units is ofconventional design. Each includes a flat strip type resistor restingagainst the inner face of the base connected thereto and to the outerterminals l8 and 20 by suitable rivets. A rotatable spring contactmember 22 is mounted on the milled end of each of shafts 24, 24a, 26,and 26a and rotates therewith. This member has fingers which ride on theresistor strip to vary the resistance when the shafts are rotated. Thereis also mounted on the milled end of these shafts a stop plate 28 whichlimits the rotation of the shafts to an angular amount of approximatelytwo hundred and sixty degrees. The spring contact member 22 and stopplate 28 may be secured in place by staking over the end of the shaft. Amidc'le terminal 30 riveted to the base of the housings i2 is connectedby a pig-tail connector 32 to the spring contactor 22 so that the unitmay be electrically connected in a desired circuit. The shaft with thespring contact member and stop plate in place are inserted in thebearing 14 from the inner end and held against axial movement by aC-ring 34. The shafts 24 and 26 are solid. However, the shaft 24 has aslot 36 in its forward end substantially parallel with the milled flatswhile the shaft 26 has a slot 38 in its rear end substantially at ninetydegrees to the milled flats. These slots accommodate the flanges oncoupling 40 (Figure 4) and thus the units are connected for tandemmovement. Shaft 26 is somewhat longer than shaft 24 and has additionalmilled flats on its forward end on which control knob 42 is fixedly heldby a hex screw 44. Rotation of knob 42 results in joint adjustment ofboth resistances of the resistor. It is necessary that the terminals i8,28 and 30 of the front unit project radially from the rear of thehousing to bring the units close together. However, the terminals I8,28, and 30 for the rear unit may either project radially or axially fromthe rear of the housing, although the latter arrangement is moreconvenient when connecting wires to the terminals.

In order to rigidly secure and hold the rear unit to the rear of thefront unit and to provide space for the coupler 49 there is insertedbetween the units a spacing disc 46 which may be made of plastic orother non-conductive material. spacing disc 46 seats on the edges of theopening of the rear unit and also acts. as a cover for the housing ofthat unit. The face of the disc has recesses 48 to accommodate theterminals I8, 20, and 38 and their rivets and recesses 49 to provideroom for the mounting brackets 52 and 54. It also has a central apertureto provide operating The space for the coupler 40. Around the edge ofthis aperture there is a recess 50 for accommodating the ridges on therear surface of the base of the housings l2. The two units are arrangedand held in coaxial position by mounting brackets 52 and 54 and tiebrackets 56 and 58. The mounting brackets 52 and 54 projectdiametrically radially from the rear wall or base of the forward unitbeing held to the face thereof by rivets. The tie brackets 56 and 58have body portions resting fiat against and riveted to the base or rearwall of the rear unit and legs closely paralleling the sides of the rearhousing and projecting forwardly into engagement with the mountingbrackets 52 and 54. The ends of the legs project through slots in themounting brackets and are staked or bent over as indicated at 60 to holdthe legs to the mounting brackets. The legs may be secured by othermeans, such assoldering or welding, so long as the connection is madewhile the units are held tightly together. This manner ofinter-connecting the units conserves the greatest amount of axial anddiametrical space and is of considerable importance when it isconsidered that each unit has an overall diameter (exclusive of the knobterminals and mounting bracket and tie brack t) of only approximately.615 to .619 inch.

In the device shown in Figures 5 to 8, each of 4 the units is separatelyoperated by its own control knob so that the multiple resistor has dualrather than tandem control. Each of the resistor units I2 is fastenedtogether in the same manner as hereinbefore described for the tandemcontrol unit. The main difference resides in the provision of a bore 62in the rear unit shaft 24a and a bore 64 in the front unit shaft 25a.The shaft 26a also has an extension 66 provided with milled flats, whichpermit the knoblocking clip 68 to slide thereon, and a retaining groove6?. Before the rear unit is assembled to the front unit a coupling shaft10 (see Figure 8) is inserted through the counter bore 64 so that itscoupling end is at the rear end of the shaft 26a. The coupling head ofthis shaft interlocks with the slot 72 in the forward end of shaft 24a.To keep the dual control unit at a minimum length it is necessary toprovide a compact manner for mounting the control knobs on theirrespective shafts. The inner knob 14 has an oblong recess which receivesthe milled extension 66 to cause the shaft 26a to be rotated therewith.The knob-locking clip 68 is first fitted over the extension 65 and thenrotated ninety degrees to lock it in the groove 61, thus holding itagainst axial displacement. The knob-locking clip 68 has forwardlyprojecting arms 16 substantially normal to the plane of its body portionwhich fit through slots F8 in the knob 14; the knob being held on thearms 16 by bending over an outer corner 88 of the end of said arms. Itis more satisfactory, although not necessary, to notch,

the arms 16 near the tips so that when the corners are bent, as shown inFigure 7, a sloping edge 82 will engage the outer edge of the slots T8to stress the engagement between the knob 14 and the clip 68, thusfirmly seating the extension 66 in the recess of the knob. When the knob14 is fastened as heretofore described, a suitable cylindrical tool maybe inserted in the bore 62 and the coupling shaft 10 urged forwardly bysuch tool so that its head is flush against the rear end of shaft 26a.While so held an outer knob 84 is fitted over the end of coupling shaft10 and secured in place by the set screw and milled flat arrangementindicated at 85 and 88. It is preferable to place a thin shim betweenthe knob 74 and the knob 84 during assembly which when removed willprovide for suflicient clearance between these knobs. A recess in therear of knob 84 provides clearance space for the ends of legs 16.

Although only one embodiment of the invention is shown and describedherein, it will be understood that this application is intended to coversuch changes or modifications as come within the spirit of the inventionor scope of the following claims.

We claim:

l. In a variable resistor having a plurality of variable resistor unitsmounted in identical coaxially arranged housings, the combinationlaterally projecting mounting brackets secured to one of said housings,said mounting brackets having slots for receiving the ends of thebrackets and means by which said resistor may be mounted to a chassis orframe with tie brackets secured to an adjacent other one of saidhousings, said tie brackets having legs paralleling the sides of saidlast mentioned housing and ends projecting through said slots and stakedagainst said mounting brackets whereby said housings are maintained inprearranged relationship.

2. In a variable resistor having a plurality of variable resistor unitsmounted in identical coaxially arranged housings, the combination oflaterally projecting mounting brackets secured to the base of one ofsaid housings, said mounting brackets having means by which saidresistor may be mounted to a chassis or frame, with tie brackets securedto the base of an adjacent other one of said housings, said tie bracketshaving longitudinally extending legs paralleling the sides of the saidlast mentioned housing and ends secured to said mounting brackets tomaintain said housings in prearranged relationship.

3. In a miniature multiple unit variable resistor having each unitenclosed in identical housings, the combination of laterally projectingmounting brackets secured to the base of a first housing, with a spacingdisc forming a cover for an adjacent second housing and spacing saidfirst and second housings, there being recesses in said spacing disc toaccommodate said mounting brackets, and tie brackets secured to the baseof the second housing and extending to and engaged with said mountingbrackets.

4. In a miniature multiple unit variable resistor having coaxiallyarranged units operated by shafts, an inner knob for operating the shaftof a first unit, said knob being connected to the shaft of said firstunit by a knob-locking clip consisting of a body mounted on the shaftbetween said resistor and said inner knob, said body having spaced armsprojecting normally to the plane of the body, said inner knob havingslots through which said arms project, said arms having a bent tipholding said knob on said arms, and an outer knob secured to the shaftof a second unit, said outer knob having a recess on its inner wall foraccommodating and enclosing said bent tips.

5. In a miniature multiple unit variable resistor having coaxiallyarranged units, bored shafts for controlling said units severallyrotatably mounted in each unit, an inner knob connected to the shaft ofa first unit, a coupling shaft concentrically mounted within the bore ofsaid last-named shaft, said coupling shaft having a coupling head at itsinner end consisting of a flange extending radially of said shaft tolimit the axial movement thereof, and a key extending ou Wardly of saidflange, anouter knob mounted on the outer end of said coupling shaft, aslot in the bored shaft of a second unit for receiving said key toprovide a driving connection between said coupling shaft and said boredshaft, the bore in the shaft of the second unit having an end openingpermitting the insertion of a tool through such shaft to engage andoutwardly axially urge said coupling shaft during the assembly of saidouter knob.

KARL W. YOUNGBECK. HENRY J. GLUECKSTEIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,415,534 Donle May 9, 19221,449,725 Beckert Mar. 27, 1923 1,643,105 Wiegand Sept. 20, 19272,120,651 Schellenger June 14, 1938 2,172,396 Meuer Sept. 12, 19392,303,499 Rich Dec. 1, 1942 2401,03? Arvin May 28, 1946

